It has been revealed that ultraviolet negatively affects skin, such as causing a skin cancer and a burn when anyone is exposed to sunlight for a long time. The cosmetics containing a UV-absorbing or shielding agent have been used to prevent such skin damage. However, it is possible that when the UV-absorbing and/or shielding agent added to the cosmetics are used in a form of molecule, the agents themselves may be adsorbed into skin, causing side effects.
In order to solve the above problems, many studies have been carried out to enhance skin safety by grinding an UV-shielding agent into small particles and adding the particles into the cosmetics. That is to say, the ultraviolet shielding agent was used as a UV-protective cosmetics additive by adhering or binding physical UV-shielding materials, for example titanium oxide and zinc oxide, to silicone resin particles. However, the cosmetics obtained from the method has problems of deteriorating its inherent property as well as of using a large amount of the UV-shielding agent and causing a stress whitening effect since it has poorer lubricating and elongating properties than that obtained by using a polyorganosilsesquioxane particle mentioned later.
Accordingly, many attempts have been carried out to use organosilsesquioxane such as polymethylsilsesquioxane, which is an insoluble resin forming a compact 3D network structure of a molecular frame, having a good fluidity and showing a gloss, and used as makeup cosmetic materials due to the lubricating and elongating properties (see Japanese Patent Publication Nos. 54-72300 and 60-13813), as the UV-absorbing or shielding agent.
However, there are various problems in manufacturing a polysilsesquioxane particle. For example, Japanese Patent Publication No. 63-77940 discloses that the particle is manufactured by polycondensation reaction in the interface between two layers of organic solutions. But this method has disadvantages of being difficult to control a stirring speed and maintain the interface during the reaction, and having a slow reaction rate due to the significantly low possibility of contacting with alkali metals.
Also, Japanese Patent Publication Nos. 2000-169583 and 2004-33927 disclose a manufacturing method wherein an emulsion is prepared and then its interface is used instead of the interface of the organic solutions. But this method has disadvantages that a process itself for manufacturing the emulsion is very complex, and that it is difficult to maintain the emulsion within a constant particle size.
In addition, Japanese Patent Publication No. 10-363101 discloses a method of manufacturing particles by adding water/butanol solution to organosilanetriol or its condensates obtained by hydrolyzing organotrialkoxysilane, followed by adding the resultant mixture to an alkaline aqueous solution. But this method has problems of being difficult to obtain small-size particles and having an extended reaction time and a low productivity.
Further, Japanese Patent Publication No. 2001-192452 discloses a method of manufacturing polysilsesquioxane particles by using an acid as a catalyst in a first process, and an alkaline aqueous solution as a neutralizing agent and a polycondensation reaction catalyst in a second process by using organotrialkoxysilane. But this method has a problem of going through a complex cascade reaction.
Also, Japanese Patent Publication No. S08-27273 discloses an attempt for manufacturing polyphenylsilsesquioxane containing an aromatic substituent, for example a phenyl group, to be used as a UV-absorbing cosmetics additive. But this method is subject to a complex process for purchasing and using spherical polysilsesquioxane particle having a mean particle diameter of 0.1 to 30 μm, as well as reacting diketone compounds (for example, benzoylacetone, acetylacetone and so oil) with aminoalkylalkoxysilane or the like to manufacture a polysilsesquioxane particle. And it also has a disadvantage of inevitably increasing temperature for the reaction.